Abstract: The diluent of sample, from 4-month healthy infant’s fresh feces, were inoculated to MRS culture and incubated in anaerobic condition at 37 ℃ for 2 d . Three kinds of Lactobacillus acidophilus to produce obvious ring of dissolving calcium were screened after two days. And these Lactobacillus acidophilus were studied for physiological and biochemical properties, for example the antagonistic activity against pathogenic bacteria of metabolite and the ability of tolerance to acid and bile salts respectively. It indicated that L2 strain was optimal on all properties. The metabolite of L2 strain had a capability to resist common pathogenic bacteria. L2 strain showed resistance to defend against the environment of 0.5% bile salts and at pH 3.0 for a long time. L2 strain was preliminary identified as Lactobacillus acidophilus according to Berges bacteriology (the eighth edition). The metabolite was made of three components as being analysed by capillary electrophoresis. The molecular mass range of compo- nent 1 is 2.512～3.5 kD, and of component 2 and 3 are respectively 16.949～66.2 kD. The metabolite is senitive to part of the enzymes. By comprehensive analysis, the metabolite produced by bacteriocin L2 strain can be used as p food preservative or food additives in the future.

Key words: infant, Lactobacillus acidophilus, screening, identification